diff --git a/conf/cf-lex.l b/conf/cf-lex.l
index c99bd714..2a25e629 100644
--- a/conf/cf-lex.l
+++ b/conf/cf-lex.l
@@ -78,10 +78,8 @@ pool *global_root_scope_pool;
 linpool *global_root_scope_linpool;
 static struct sym_scope
   global_root_scope = {
-    .active = 1,
   },
   global_filter_scope = {
-    .active = 0,
     .next = &global_root_scope,
   };
 
@@ -634,7 +632,8 @@ cf_find_symbol_scope(const struct sym_scope *scope, const byte *c)
 
   /* Find the symbol here or anywhere below */
   while (scope)
-    if (scope->active && scope->hash.data && (s = HASH_FIND(scope->hash, SYM, c)))
+    if (((scope != &global_filter_scope) || !new_config || new_config->allow_attributes) &&
+	scope->hash.data && (s = HASH_FIND(scope->hash, SYM, c)))
       return s;
     else
       scope = scope->next;
@@ -735,6 +734,8 @@ ea_lex_register(struct ea_class *def)
   def->sym->attribute = def;
 }
 
+#if 0
+/* When we start to support complete protocol removal, we may need this function */
 void
 ea_lex_unregister(struct ea_class *def)
 {
@@ -743,19 +744,13 @@ ea_lex_unregister(struct ea_class *def)
   mb_free(sym);
   def->sym = NULL;
 }
+#endif
 
 struct ea_class *
 ea_class_find_by_name(const char *name)
 {
-  if (!global_filter_scope.hash.data)
-    return NULL;
-
-  struct symbol *sym = HASH_FIND(global_filter_scope.hash, SYM, name);
-
-  if (!sym || (sym->class != SYM_ATTRIBUTE))
-    return NULL;
-  else
-    return sym->attribute;
+  struct symbol *sym = cf_find_symbol_scope(config ? config->root_scope : &global_filter_scope, name);
+  return sym && (sym->class == SYM_ATTRIBUTE) ? sym->attribute : NULL;
 }
 
 void f_type_methods_register(void);
@@ -803,7 +798,6 @@ cf_lex_init(int is_cli, struct config *c)
     BEGIN(INITIAL);
 
   c->root_scope = c->current_scope = cfg_allocz(sizeof(struct sym_scope));
-  c->root_scope->active = 1;
 
   if (is_cli)
     c->current_scope->next = config->root_scope;
@@ -828,7 +822,6 @@ cf_push_scope(struct config *conf, struct symbol *sym)
 
   s->next = conf->current_scope;
   conf->current_scope = s;
-  s->active = 1;
   s->name = sym;
   s->slots = 0;
 }
@@ -844,10 +837,7 @@ void
 cf_pop_scope(struct config *conf)
 {
   ASSERT(!conf->current_scope->soft_scopes);
-
-  conf->current_scope->active = 0;
   conf->current_scope = conf->current_scope->next;
-
   ASSERT(conf->current_scope);
 }
 
@@ -903,8 +893,8 @@ cf_swap_soft_scope(struct config *conf)
 void
 cf_enter_filters(void)
 {
-  ASSERT_DIE(!global_filter_scope.active);
-  global_filter_scope.active = 1;
+  ASSERT_DIE(!new_config->allow_attributes);
+  new_config->allow_attributes = 1;
 }
 
 /**
@@ -913,8 +903,8 @@ cf_enter_filters(void)
 void
 cf_exit_filters(void)
 {
-  ASSERT_DIE(global_filter_scope.active);
-  global_filter_scope.active = 0;
+  ASSERT_DIE(new_config->allow_attributes);
+  new_config->allow_attributes = 0;
 }
 
 
diff --git a/conf/conf.c b/conf/conf.c
index d828b6df..c76046ee 100644
--- a/conf/conf.c
+++ b/conf/conf.c
@@ -60,7 +60,8 @@
 
 static jmp_buf conf_jmpbuf;
 
-struct config *config, *new_config;
+struct config *config;
+_Thread_local struct config *new_config;
 pool *config_pool;
 
 static struct config *old_config;	/* Old configuration */
diff --git a/conf/conf.h b/conf/conf.h
index b5168873..841d5c1f 100644
--- a/conf/conf.h
+++ b/conf/conf.h
@@ -58,6 +58,7 @@ struct config {
 
   struct sym_scope *root_scope;		/* Scope for root symbols */
   struct sym_scope *current_scope;	/* Current scope where we are actually in while parsing */
+  int allow_attributes;			/* Allow attributes in the current state of configuration parsing */
   _Atomic int obstacle_count;		/* Number of items blocking freeing of this config */
   event done_event;			/* Called when obstacle_count reaches zero */
   int shutdown;				/* This is a pseudo-config for daemon shutdown */
@@ -67,7 +68,7 @@ struct config {
 
 /* Please don't use these variables in protocols. Use proto_config->global instead. */
 extern struct config *config;		/* Currently active configuration */
-extern struct config *new_config;	/* Configuration being parsed */
+extern _Thread_local struct config *new_config;	/* Configuration being parsed */
 
 struct config *config_alloc(const char *name);
 int config_parse(struct config *);
@@ -149,7 +150,6 @@ struct sym_scope {
 
   uint slots;				/* Variable slots */
   byte soft_scopes;			/* Number of soft scopes above */
-  byte active:1;			/* Currently entered */
   byte block:1;				/* No independent stack frame */
   byte readonly:1;			/* Do not add new symbols */
 };
diff --git a/doc/bird.sgml b/doc/bird.sgml
index c8cebffe..6e5a596d 100644
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -3313,6 +3313,13 @@ some of them (marked with `<tt/O/') are optional.
 	name="local Role"> is configured it set automatically.
 </descrip>
 
+<p>For attributes unknown by BIRD, the user can assign a name (on top level)
+to an attribute by its number. This defined name can be used then to both set
+(by a bytestring literal, transitive) or unset the given attribute even though
+BIRD knows nothing about it:
+
+<tt><label id="bgp-attribute-custom">attribute bgp <m/number/ bytestring <m/name/;</tt>
+
 <sect1>Example
 <label id="bgp-exam">
 
diff --git a/filter/config.Y b/filter/config.Y
index 76e80436..f27d9f58 100644
--- a/filter/config.Y
+++ b/filter/config.Y
@@ -28,6 +28,8 @@ static struct f_method_scope {
 } f_method_scope_stack[32];
 static int f_method_scope_pos = -1;
 
+static struct sym_scope *f_for_stored_scope;
+
 #define FM  (f_method_scope_stack[f_method_scope_pos])
 
 static inline void f_method_call_start(struct f_inst *object)
@@ -41,13 +43,14 @@ static inline void f_method_call_start(struct f_inst *object)
   if (!scope)
     cf_error("No methods defined for type %s", f_type_name(object->type));
 
+  /* Replacing the current symbol scope with the appropriate method scope
+     for the given type. */
   FM = (struct f_method_scope) {
     .object = object,
     .main = new_config->current_scope,
     .scope = {
       .next = NULL,
       .hash = scope->hash,
-      .active = 1,
       .block = 1,
       .readonly = 1,
     },
@@ -57,22 +60,16 @@ static inline void f_method_call_start(struct f_inst *object)
 
 static inline void f_method_call_args(void)
 {
-  ASSERT_DIE(FM.scope.active);
-  FM.scope.active = 0;
-
+  /* For argument parsing, we need to revert back to the standard symbol scope. */
   new_config->current_scope = FM.main;
 }
 
 static inline void f_method_call_end(void)
 {
   ASSERT_DIE(f_method_scope_pos >= 0);
-  if (FM.scope.active) {
-    ASSERT_DIE(&FM.scope == new_config->current_scope);
+  if (&FM.scope == new_config->current_scope)
     new_config->current_scope = FM.main;
 
-    FM.scope.active = 0;
-  }
-
   f_method_scope_pos--;
 }
 
@@ -423,14 +420,18 @@ filter_eval:
 
 conf: custom_attr ;
 custom_attr: ATTRIBUTE type symbol ';' {
-  if (($3->class == SYM_ATTRIBUTE) && ($3->scope == new_config->root_scope))
-    cf_error("Duplicate attribute %s definition", $3->name);
-
-  cf_define_symbol(new_config, $3, SYM_ATTRIBUTE, attribute,
-      ea_register_alloc(new_config->pool, (struct ea_class) {
+  cf_enter_filters();
+  struct ea_class *ac = ea_class_find_by_name($3->name);
+  cf_exit_filters();
+  if (ac && (ac->type == $2))
+    ea_ref_class(new_config->pool, ac);
+  else
+    ac = ea_register_alloc(new_config->pool, (struct ea_class) {
 	.name = $3->name,
 	.type = $2,
-	})->class);
+    })->class;
+
+  cf_define_symbol(new_config, $3, SYM_ATTRIBUTE, attribute, ac);
 };
 
 conf: bt_test_suite ;
@@ -1003,7 +1004,15 @@ cmd:
      new_config->current_scope->slots += 2;
    } for_var IN
    /* Parse term in the parent scope */
-   { new_config->current_scope->active = 0; } term { new_config->current_scope->active = 1; }
+   {
+     ASSERT_DIE(f_for_stored_scope == NULL);
+     f_for_stored_scope = new_config->current_scope;
+     new_config->current_scope = new_config->current_scope->next;
+   } term {
+     ASSERT_DIE(f_for_stored_scope);
+     new_config->current_scope = f_for_stored_scope;
+     f_for_stored_scope = NULL;
+   }
    DO cmd {
      cf_pop_block_scope(new_config);
      $$ = f_for_cycle($3, $6, $9);
diff --git a/filter/decl.m4 b/filter/decl.m4
index 2cb09f28..0d3b83fe 100644
--- a/filter/decl.m4
+++ b/filter/decl.m4
@@ -424,7 +424,7 @@ m4_undivert(112)
   }
 
 FID_METHOD_SCOPE_INIT()m4_dnl
-  [INST_METHOD_OBJECT_TYPE] = { .active = 1, },
+  [INST_METHOD_OBJECT_TYPE] = {},
 FID_METHOD_REGISTER()m4_dnl
   method = lp_allocz(global_root_scope_linpool, sizeof(struct f_method) + INST_METHOD_NUM_ARGS * sizeof(enum btype));
   method->new_inst = f_new_method_]]INST_NAME()[[;
diff --git a/filter/f-inst.c b/filter/f-inst.c
index 6baa1fcb..8bbb0491 100644
--- a/filter/f-inst.c
+++ b/filter/f-inst.c
@@ -878,8 +878,8 @@
 	bug("Unsupported attribute type");
 
       switch (da->type) {
-      case T_OPAQUE:
       case T_IFACE:
+      case T_OPAQUE:
 	runtime( "Setting opaque attribute is not allowed" );
 	break;
 
diff --git a/filter/f-inst.h b/filter/f-inst.h
index a476c998..82767a92 100644
--- a/filter/f-inst.h
+++ b/filter/f-inst.h
@@ -116,6 +116,7 @@ static inline struct f_static_attr f_new_static_attr(btype type, int code, int r
 { return (struct f_static_attr) { .type = type, .sa_code = code, .readonly = readonly }; }
 struct f_inst *f_generate_roa_check(struct rtable_config *table, struct f_inst *prefix, struct f_inst *asn);
 
+
 /* Hook for call bt_assert() function in configuration */
 extern void (*bt_assert_hook)(int result, const struct f_line_item *assert);
 
diff --git a/filter/filter_test.c b/filter/filter_test.c
index aa325aef..65b2e4f0 100644
--- a/filter/filter_test.c
+++ b/filter/filter_test.c
@@ -25,9 +25,9 @@
 
 
 static int
-t_reconfig(void)
+t_reconfig(const void *arg)
 {
-  if (!bt_config_file_parse(BT_CONFIG_FILE))
+  if (!bt_config_file_parse(arg))
     return 0;
 
   struct symbol *s;
@@ -79,7 +79,9 @@ main(int argc, char *argv[])
   if (!bt_config_file_parse(BT_CONFIG_FILE))
     abort();
 
-  bt_test_suite_extra(t_reconfig, 0, BT_TIMEOUT, "Testing reconfiguration");
+  bt_test_suite_arg_extra(t_reconfig, BT_CONFIG_FILE ".overlay", 0, BT_TIMEOUT, "Testing reconfiguration to overlay");
+  bt_test_suite_arg_extra(t_reconfig, BT_CONFIG_FILE, 0, BT_TIMEOUT, "Testing reconfiguration back");
+  bt_test_suite_arg_extra(t_reconfig, BT_CONFIG_FILE, 0, BT_TIMEOUT, "Testing reconfiguration to the same file");
 
   struct f_bt_test_suite *t;
   WALK_LIST(t, config->tests)
diff --git a/filter/test.conf.overlay b/filter/test.conf.overlay
new file mode 100644
index 00000000..5967ba90
--- /dev/null
+++ b/filter/test.conf.overlay
@@ -0,0 +1,3 @@
+attribute int peek_a_boo;
+
+include "test.conf";
diff --git a/lib/route.h b/lib/route.h
index f0934f06..cb1e3f4e 100644
--- a/lib/route.h
+++ b/lib/route.h
@@ -305,6 +305,7 @@ struct ea_class_ref {
 
 void ea_register_init(struct ea_class *);
 struct ea_class_ref *ea_register_alloc(pool *, struct ea_class);
+struct ea_class_ref *ea_ref_class(pool *, struct ea_class *);	/* Reference for an attribute alias */
 
 #define EA_REGISTER_ALL_HELPER(x)	ea_register_init(x);
 #define EA_REGISTER_ALL(...)		MACRO_FOREACH(EA_REGISTER_ALL_HELPER, __VA_ARGS__)
diff --git a/nest/cmds.c b/nest/cmds.c
index 4805b5a2..7984f088 100644
--- a/nest/cmds.c
+++ b/nest/cmds.c
@@ -54,9 +54,6 @@ cmd_show_symbols(struct sym_show_data *sd)
     for (const struct sym_scope *scope = config->root_scope; scope; scope = scope->next)
       HASH_WALK(scope->hash, next, sym)
       {
-	if (!sym->scope->active)
-	  continue;
-
 	if (sd->type && (sym->class != sd->type))
 	  continue;
 
diff --git a/nest/rt-attr.c b/nest/rt-attr.c
index 0457e68a..201dff30 100644
--- a/nest/rt-attr.c
+++ b/nest/rt-attr.c
@@ -573,16 +573,20 @@ static struct idm ea_class_idm;
 
 /* Config parser lex register function */
 void ea_lex_register(struct ea_class *def);
-void ea_lex_unregister(struct ea_class *def);
 
 static void
 ea_class_free(struct ea_class *cl)
 {
+  RTA_LOCK;
+
   /* No more ea class references. Unregister the attribute. */
   idm_free(&ea_class_idm, cl->id);
   ea_class_global[cl->id] = NULL;
-  if (!cl->hidden)
-    ea_lex_unregister(cl);
+
+  /* When we start supporting full protocol removal, we may need to call
+   * ea_lex_unregister(cl), see where ea_lex_register() is called. */
+
+  RTA_UNLOCK;
 }
 
 static void
@@ -619,7 +623,7 @@ ea_class_init(void)
       sizeof(*ea_class_global) * (ea_class_max = EA_CLASS_INITIAL_MAX));
 }
 
-static struct ea_class_ref *
+struct ea_class_ref *
 ea_ref_class(pool *p, struct ea_class *def)
 {
   def->uc++;
@@ -640,9 +644,6 @@ ea_register(pool *p, struct ea_class *def)
   ASSERT_DIE(def->id < ea_class_max);
   ea_class_global[def->id] = def;
 
-  if (!def->hidden)
-    ea_lex_register(def);
-
   return ea_ref_class(p, def);
 }
 
@@ -680,7 +681,12 @@ ea_register_init(struct ea_class *clp)
 {
   RTA_LOCK;
   ASSERT_DIE(!ea_class_find_by_name(clp->name));
-  ea_register(&root_pool, clp);
+
+  struct ea_class *def = ea_register(&root_pool, clp)->class;
+
+  if (!clp->hidden)
+    ea_lex_register(def);
+
   RTA_UNLOCK;
 }
 
diff --git a/proto/bgp/attrs.c b/proto/bgp/attrs.c
index dfd6f1d3..510456e8 100644
--- a/proto/bgp/attrs.c
+++ b/proto/bgp/attrs.c
@@ -1223,8 +1223,8 @@ bgp_register_attrs(void)
     if (!bgp_attr_table[i].name)
       bgp_attr_table[i] = (union bgp_attr_desc) {
 	.name = mb_sprintf(&root_pool, "bgp_unknown_0x%02x", i),
-	.type = T_OPAQUE,
-	.flags = BAF_OPTIONAL,
+	.type = T_BYTESTRING,
+	.flags = BAF_OPTIONAL | BAF_TRANSITIVE,
 	.readonly = 1,
 	.export = bgp_export_unknown,
 	.encode = bgp_encode_raw,
@@ -1236,6 +1236,12 @@ bgp_register_attrs(void)
   }
 }
 
+struct ea_class *
+bgp_find_ea_class_by_id(uint id)
+{
+  return (id < ARRAY_SIZE(bgp_attr_table)) ? &bgp_attr_table[id].class : NULL;
+}
+
 
 /*
  *	Attribute export
diff --git a/proto/bgp/bgp.h b/proto/bgp/bgp.h
index 997c8456..079a98ea 100644
--- a/proto/bgp/bgp.h
+++ b/proto/bgp/bgp.h
@@ -662,6 +662,7 @@ bgp_total_aigp_metric(const rte *e)
 }
 
 void bgp_register_attrs(void);
+struct ea_class *bgp_find_ea_class_by_id(uint id);
 
 
 /* packets.c */
diff --git a/proto/bgp/config.Y b/proto/bgp/config.Y
index 963bd724..b0a2df33 100644
--- a/proto/bgp/config.Y
+++ b/proto/bgp/config.Y
@@ -335,6 +335,19 @@ bgp_channel_end:
 
 bgp_proto_channel: bgp_channel_start bgp_channel_opt_list bgp_channel_end;
 
+custom_attr: ATTRIBUTE BGP NUM type symbol ';' {
+  if ($3 > 255 || $3 < 1)
+    cf_error("Invalid attribute number. (Given %i, must be 1-255.)", $3);
+
+  struct ea_class *ac = bgp_find_ea_class_by_id($3);
+  ASSERT_DIE(ac);
+  if ($4 != ac->type)
+    cf_error("Attribute %d type must be %s, not %s.", $3, f_type_name(ac->type), f_type_name($4));
+
+  ea_ref_class(new_config->pool, ac);
+  cf_define_symbol(new_config, $5, SYM_ATTRIBUTE, attribute, ac);
+};
+
 CF_ENUM(T_ENUM_BGP_ORIGIN, ORIGIN_, IGP, EGP, INCOMPLETE)
 
 CF_CODE